Process for the producing of hard polyurethane foams with low heat conductivity

ABSTRACT

A process for the production of rigid polyurethane foams having low thermal conductivity is described. This process comprises reacting 
     A) a polyol component comprising: 
     (1) at least one polyester polyol having a molecular weight of from 100 to 30,000 g/mol and containing at least two isocyanate-reactive hydrogen atoms; 
     (2) at least one polyether polyol having a molecular weight of from 150 to 12,500 g/mol and containing at least two isocyanate-reactive hydrogen atoms and at least one tertiary nitrogen atom, and being prepared from a starter compound comprising ammonia or a compound containing at least one primary, secondary or tertiary amino group; 
     (3) at least one polyether polyol having a molecular weight of from 150 to 12,500 g/mol and containing at least two isocyanate-reactive hydrogen atoms, and being prepared from a starter compound comprising water or a polyhydric alcohol; 
     (4) at least one catalyst; 
     (5) water 
     (6) at least one blowing agent; and, optionally 
     (7) auxiliary substances and/or additives; with 
     B) an organic polyisocyanate having an NCO group content of from 20 to 48% by weight. 
     Cyclopentane blown rigid polyurethane foams which exhibit low thermal conductivity and the end-use of such foams as an interlayer in a process for the production of composite components and for filling cavities is also disclosed.

This invention relates to a novel process for the production ofsubstantially closed-cell rigid polyurethane foams.

Due to their low thermal conductivity, rigid polyurethane foams are usedfor insulation applications in refrigeration and freezing appliances, inindustrial equipment, tank farms, pipelines, shipbuilding and in theconstruction industry. A summary review of the production of rigidpolyurethane foams and the use thereof is given in Kunststoff-Handbuch,volume 7 (Polyurethane), 2nd edition 1983, edited by Dr. Günter Oertel(Carl Hanser Verlag, Munich).

The thermal conductivity of a largely closed-cell rigid polyurethanefoam is largely dependent upon the nature of the blowing agent or cellgas used. Completely halogenated chlorofluorocarbons (CFCs),inparticular trichlorofluoromethane (R11), which has particularly lowthermal conductivity, had proved particularly suitable for this purpose.These substances are chemically inert and non-toxic. However, due totheir elevated stability, completely halogenated chlorofluorocarbonsreach the stratosphere, where, due to their chlorine content, they playa part in breaking down the ozone present there (for example Molina,Rowland, Nature 249 (1974) 810; first interim report of the GermanParliament's commission of enquiry, Vorsorge zum Schutz derErdatmosphäre [precautions for the protection of the earth's atmosphere]of 02.11.1988, German Parliament, public relations department, Bonn).

Formulations containing a lower R11 concentration have been proposed inorder to reduce the R11 content in rigid polyurethane foams.

It has also be proposed (for example EP 344 537, U.S. Pat. No.4,931,482) to use partially fluorinated hydrocarbons(hydrofluoroalkanes) which still contain at least one carbon-hydrogenbond as a blowing agent. Substances from this class of compounds containno chlorine atoms and thus have a ODP value (ozone depletion potential)of zero (by way of comparison: R11: ODP=1). Typical representatives ofthis class of substances are, for example: 1,1,1,4,4,4-hexafluorobutane(R356) or 1,1,1,3,3-pentafluoropropane (245fa).

It is furthermore known to use hydrocarbons, either pure or as a mixture(U.S. Pat. No. 5,391,317), such as n- or i-pentane, 2,2-dimethylbutane,cyclopentane or cyclohexane as blowing agents. It is also known to usehydrocarbons in conjunction with water as blowing agents (EP 0 421 269).

It is moreover known that, by virtue of their chemical structure,unsubstituted hydrocarbons are highly non-polar and thus mix very poorlywith the polyols conventionally used in rigid foam production. Completemiscibility is, however, an important prerequisite for the conventionalproduction technique in which the polyol and isocyanate components aremechanically foamed. In addition to the reactive polyether- orpolyesterpolyols, the polyol component also contains blowing agents andauxiliaries such as activators, emulsifiers and stabilisers in dissolvedform. It is known that polyol formulations containing aminopolyethersexhibit particularly high alkane solubility (WO 94/03515).

It is also known that hydrocarbon-blown rigid foams have poorer thermalconductivities than rigid foams blown with R11 or with reducedquantities of R11, which is due to the higher thermal conductivities ofhydrocarbon gases. (Thermal conductivities of the gases at 20° C.: R11:8 mW/mK; cyclopentane: 10 mW/mK; n-pentane, 13 mW/mK; i-pentane, 13mW/mK).

The object of the present invention was to provide hydrocarbon-blownrigid polyurethane foams which have thermal conductivities of the samelow level as foams blown with reduced quantities of R11.

It has surprisingly been found that polyol formulations based on acertain polyol mixture yield foams having thermal conductivities whichare at the same, low level as foams blown with reduced quantities ofR11, in particular if cyclopentane is used as the blowing agent.

The present invention accordingly provides a process for the productionof rigid polyurethane foams having low thermal conductivity from polyolsand polyisocyanates together with blowing agents and optionally foamauxiliaries, characterised in that the rigid polyurethane foam isobtained by reacting

A. a polyol component containing

1. at least one polyesterpolyol of a molecular weight of 100 to 30000g/mol having at least two isocyanate-reactive hydrogen atoms,

2. compounds of a molecular weight from 150 to 12500 g/mol containing atleast two isocyanate-reactive hydrogen atoms, the molecules of whichcompounds contain at least one tertiary nitrogen atom,

3. compounds of a molecular weight from 150 to 12500 g/mol containing atleast two isocyanate-reactive hydrogen atoms,

4. catalysts,

5. water,

6. blowing agent and

7. optionally auxiliary substances and additives with

B. an organic and/or modified organic polyisocyanate having an NCOcontent of 20 to 48 wt. %.

It is surprising that the combination according to the invention of apolyesterpolyol with the stated aminopolyethers and a further polyol inthe polyol component of hydrocarbon-blown foams should result in such alow thermal conductivity.

Polyol formulations according to the invention contain at least onepolyesterpolyol of the molecular weight from 100 to 30000 g/mol,preferably of 150 to 10000 g/mol, particularly preferably of 200 to 600g/mol, prepared from aromatic and/or aliphatic mono-, di- ortricarboxylic acids and polyols containing at least two hydroxyl groups.Examples of dicarboxylic acids are phthalic acid, fumaric acid, maleicacid, azelaic acid, glutaric acid, adipic acid, suberic acid,terephthalic acid, isophthalic acid, decanedicarboxylic acid, malonicacid, glutaric acid, succinic acid and fatty acids such as stearic acid,oleic acid, ricinoleic acid. Both the pure mono-, di- or tricarboxylicacids and any desired mixtures thereof may be used. Instead of the freemono-, di- and tricarboxylic acids, it is also possible to use thecorresponding mono-, di- and tricarboxylic acid derivatives, such as forexample mono-, di- and tricarboxylic acid esters of alcohols having 1 to4 carbon atoms or mono-, di- and tricarboxylic anhydrides ortriglycerides. The following are preferably used as the alcoholcomponent for esterification: ethylene glycol, diethylene glycol,triethylene glycol, tetraethylene glycol, 1,2- or 1,3-propanediol,1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol,glycerol, trimethylolpropane or mixtures thereof.

According to the invention, polyol formulations may also containpolyether esters, as may, for example, be obtained by reacting phthalicanhydride with diethylene glycol and subsequently with ethylene oxide(EP-A 0 250 967).

Polyol formulations according to the invention contain at least onecompound of the molecular weight from 150 to 12500 g/mol, preferably of200 to 1500 g/mol, containing at least two isocyanate-reactive hydrogenatoms, the molecules of which compound contain at least one tertiarynitrogen atom. These compounds are obtained by polyaddition of alkyleneoxides, such as for example ethylene oxide, propylene oxide, butyleneoxide, dodecyl oxide or styrene oxide, preferably propylene oxide orethylene oxide, onto starter compounds. The starter compounds used areammonia or compounds containing at least one primary or secondary ortertiary amino group, such as for example aliphatic amines such asethylenediamine, ethylenediamine oligomers (for examplediethylenetriamine, triethylenetetramine or pentaethylenehexamine),ethanolamine, diethanolamine, triethanolamine, N- methyl- orN-ethyldiethanolamine, 1,3-propylenediamine, 1,3- or1,4-butylenediamine, 1,2-, 1,3-, 1,4-, 1,5-, 1,6-hexamethylenediamine,aromatic amines such as phenylenediamines, tolylenediamines(2,3-tolylenediamine, 3,4-tolylenediamine, 2,4-tolylenediamine,2,5-tolylenediamine, 2,6-tolylenediamine or mixtures of the statedisomers), 2,2′-diaminodiphenylmethane, 2,4′-diaminodiphenylmethane,4,4′-diaminodiphenylmethane or mixtures of these isomers.

Polyol formulations according to the invention moreover contain at leastone compound of the molecular weight from 150 to 12500 g/mol, preferablyof 200 to 1500 g/mol, containing at least two isocyanate-reactivehydrogen atoms. These compounds are obtained by polyaddition of alkyleneoxides, such as for example ethylene oxide, propylene oxide, butyleneoxide, dodecyl oxide or styrene oxide, preferably propylene oxide orethylene oxide, onto starter compounds. The starter compounds used arepreferably water and polyhydric alcohols such as sucrose, sorbitol,pentaerythritol, trimethylolpropane, glycerol, propylene glycol,ethylene glycol, diethylene glycol together with mixtures of the statedstarter compounds. These polyols which are also to be used according tothe invention advantageously allow the rigid polyurethane foams toachieve the mechanical properties which are conventionally required inpractice.

Polyol formulations according to the invention contain an activator oran activator mixture, which results in a fibre time of 20 to 50 s,preferably of 25 to 45 s, particularly preferably of 27 to 40 s iffoaming is performed at 20° C. using a Hennecke HK 270 high pressuremachine. The fibre time extends from the time of mixing to the momentfrom which a rod introduced into the foam draws fibres when withdrawn.

According to the invention, the catalysts conventional in polyurethanechemistry may be used. Examples of such catalysts are:triethylenediamine, N,N-dimethylcyclohexylamine, tetramethylenediamine,1-methyl-4-dimethylaminoethylpiperazine, triethylamine, tributylamine,dimethylbenzylamine,N,N′,N″-tris-(dimethylaminopropyl)hexahydrotriazine,dimethylaminopropylformamide, N,N,N′,N′-tetramethylethylenediamine,N,N,N′,N′-tetramethylbutanediamine, tetramethylhexanediamine,pentamethyldiethylenetriamine, tetramethyldiaminoethyl ether,dimethylpiperazine, 1,2-dimethylimidazole, 1-azabicyclo(3.3.0)octane,bis-(dimethylaminopropyl)urea, bis-(dimethylaminopropyl) ether,N-methylmorpholine, N-ethylmorpholine, N-cyclohexylmorpholine,2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, triethanolamine,diethanolamine, triisopropanolamine, N-methyldiethanolamine,N-ethyldiethanolamine, dimethylethanolamine, tin(II) acetate, tin(II)octoate, tin(II) ethylhexoate, tin(II) laurate, dibutyltin diacetate,dibutyltin dilaurate, dibutyltin maleate, dioctyltin diacetate,tris-(N,N-dimethylaminopropyl)-s-hexahydrotriazine, tetramethylammoniumhydroxide, sodium acetate, potassium acetate, sodium hydroxide ormixtures of these or similar catalysts.

Polyol formulations according to the invention contain 0.5 to 7.0 partsby weight, preferably 1.0 to 3.0 parts by weight of water per 100 partsby weight of polyol component A.

Alkanes such as cyclohexane, cyclopentane, i-pentane, n-pentane,n-butane, isobutane, 2,2-dimethylbutane and mixtures of the statedblowing agents are used according to the invention.

Aromatic polyisocyanates, as are for example described by W. Siefken inJustus Liebigs Annalen der Chemie, 562, pages 75 to 136, [are used], forexample, as the isocyanate component, for example those of the formula

Q(NCO)_(n),

in which

n means 2 to 4, preferably 2, and

Q means an aliphatic hydrocarbon residue having 2 to 18, preferably 6 to10, C atoms, a cycloaliphatic hydrocarbon residue having 4 to 15,preferably 5 to 10, C atoms, an aromatic hydrocarbon residue having 8 to15, preferably 8 to 13, C atoms, for example such polyisocyanates as aredescribed in DE-OS 28 32 253, pages 10 to 11.

The industrially readily available polyisocyanates are generallyparticularly preferred, for example 2,4- and 2,6-tolylene diisocyanateand any desired mixtures of these isomers (“TDI”),polyphenylpolymethylene polyisocyanates, as are produced byaniline/formaldehyde condensation and subsequent phosgenation (“crudeMDI”) and polyisocyanates containing carbodiimide groups, urethanegroups, allophanate groups, isocyanurate groups, urea groups or biuretgroups (“modified polyisocyanates”), in particular modifiedpolyisocyanate derived from 2,4- and 2,6-tolylene diisocyanate or from4,4′- and/or 2,4′-diphenylmethane diisocyanate.

It is also possible to use prepolymers prepared from the statedisocyanates and organic compounds having at least one hydroxyl group,such as for example polyol or polyester components containing 1 to 4hydroxyl groups and of a molecular weight of 60 to 1400 g/mol.

Paraffins or fatty alcohols or dimethylpolysiloxanes together withpigments or dyes, as well as stabilisers against ageing and weathering,plasticisers and substances having a fungistatic and bacteriostaticaction, together with fillers such as barium sulphate, diatomaceousearth, carbon black or prepared chalk may also be used.

Further examples of substances optionally also used according to theinvention such as surface-active additives and foam stabilisers,together with cell regulators, reaction inhibitors, stabilisers, flameretardant substances, dyes and fillers, together with fungistaticallyand bacteriostatically active substances, together with details relatingto the manner of use and mode of action of these additives are describedin Kunststoff-Handbuch, volume VII, edited by Vieweg and Höchtlen, CarlHanser Verlag, Munich 1966, for example on pages 121 to 205, and 2ndedition 1983, edited by G. Oertel (Carl Hanser Verlag, Munich).

According to the invention, foaming during foam production may also beperformed in closed moulds. In this case, the reaction mixture isintroduced into a mould. Mould materials which may be considered aremetal, for example aluminium, or plastic, for example epoxy resin. Thefoamable reaction mixture foams in the mould and forms the moulding.Mould foaming may be performed in such a manner that the moulding has acellular structure on its surface. It may, however, also be performed insuch a manner that the moulding has a compact skin and a cellular core.According to the invention, the method used in the first case is tointroduce a quantity of reaction mixture into the mould such that theresultant foam exactly fills the mould. The method used in the lattercase involves introducing more foamable reaction mixture into the mouldthan is necessary to fill the mould cavity with foam. In the lattercase, “overcharging” is thus used, such a process being known, forexample, from U.S. Pat. Nos. 3,178,490 and 3,182,104.

The present invention also provides the use of the rigid foams producedaccording to the invention as an interlayer for composite components andfor filling cavities, especially in the production of refrigerationequipment.

The process according to the invention is preferably used for fillingcavities in refrigeration and freezing appliances. The foams may ofcourse also be produced by slab foaming or using the per se known twinconveyor belt process.

The rigid foams obtainable according to the invention are used, forexample, in the construction sector, and for insulating district heatingpipes and transport containers.

The following examples are intended to illustrate the invention, butwithout restricting the scope thereof.

In all the Examples, the rigid polyurethane foams were produced at 20°C. in a Hennecke HK 270 high pressure machine.

The fibre times stated in the individual examples were determined in thefollowing manner: the fibre time extends from the time of mixing to themoment from which a rod introduced into the foam draws fibres whenwithdrawn.

Polyol A: Polypropylene oxide polyether of molecular weight 600 based onsucrose/glycerol

Polyol B: Polypropylene oxide polyether of molecular weight 1000 basedon propylene glycol

Polyol C: Polypropylene oxide polyether of molecular weight 630 based onsucrose/propylene glycol

Polyol D: Polypropylene oxide polyether of molecular weight 370 based onglycerol

Polyol E: Polypropylene oxide polyether of molecular weight 345 based onethylenediamine

Polyol F: Polypropylene oxide polyether of molecular weight 440 based ontrimethylolpropane

Polyol G: Polyether ester of molecular weight 375 based on phthalicanhydride, diethylene glycol and ethylene oxide

Polyol H: Polypropylene oxide polyether of molecular weight 1120 basedon triethanolamine

Polyol I: Polypropylene oxide polyether of molecular weight 560 based ono-tolylenediamine

Polyol K: Polypropylene oxide polyether of molecular weight 275 based onethylenediamine

EXAMPLE 1

(not according to the invention)

Formulation for rigid polyurethane foam

Component A

80 parts by weight of polyol A

20 parts by weight of polyol B

3.5 parts by weight of water

2.0 parts by weight of silicone stabiliser

3.5 parts by weight of activator mixture consisting of activatorDesmorapid PV (Bayer AG), activator Desmorapid 726b (Bayer AG) andpotassium acetate (25%) in diethylene glycol

100 parts by weight of component A are mixed at 20° C. with 17 parts byweight of CFC R11 and 145 parts by weight of crude MDI (Desmodur 44V20,Bayer AG) and compacted to 32 kg/m³ in a closed mould.

EXAMPLE 2

(not according to the invention)

Formulation for rigid polyurethane foam

Component A

55 parts by weight of polyol C

25 parts by weight of polyol D

20 parts by weight of polyol E

2.0 parts by weight of water

2.0 parts by weight of silicone stabiliser

2.0 parts by weight of activator mixture consisting of activatorDesmorapid PV (Bayer AG) and activator Desmorapid 726b (Bayer AG)

100 parts by weight of component A are mixed at 20° C. with 12 parts byweight of cyclopentane (Erdölchemie) and 151 parts by weight of crudeMDI (Desmodur 44V20, Bayer AG) and compacted to 38 kg/m³ in a closedmould.

EXAMPLE 3

(not according to the invention)

Formulation for rigid polyurethane foam

Component A

50 parts by weight of polyol A

40 parts by weight of polyol F

10 parts by weight of polyol G

2.0 parts by weight of water

2.0 parts by weight of silicone stabiliser

2.5 parts by weight of activator mixture consisting of activatorDesmorapid PV (Bayer AG) and activator Desmorapid 726b (Bayer AG)

100 parts by weight of component A are mixed at 20° C. with 13 parts byweight of cyclopentane (Erdölchemie) and 148 parts by weight of crudeMDI (Desmodur 44V20, Bayer AG) and compacted to 38 kg/m³ in a closedmould.

EXAMPLE 4

(not according to the invention)

Formulation for rigid polyurethane foam

Component A

50 parts by weight of polyol C

25 parts by weight of polyol E

25 parts by weight of polyol H

2.2 parts by weight of water

2.0 parts by weight of silicone stabiliser

1.5 parts by weight of activator mixture consisting of activatorDesmorapid PV (Bayer AG) and activator Desmorapid 726b (Bayer AG)

100 parts by weight of component A are mixed at 20° C. with 11 parts byweight of i,n-pentane (8:3) and 142 parts by weight of crude MDI(Desmodur 44V20, Bayer AG) and compacted to 36 kg/m³ in a closed mould.

EXAMPLE 5

(not according to the invention)

Formulation for rigid polyurethane foam

Component A

55 parts by weight of polyol C

20 parts by weight of polyol D

25 parts by weight of polyesterpolyol Stepanpol® 2352 (Stepan)

2.1 parts by weight of water

2.0 parts by weight of silicone stabiliser

1.5 parts by weight of activator mixture consisting of activatorDesmorapid PV (Bayer AG) and activator Desmorapid 726b (Bayer AG)

100 parts by weight of component A are mixed with 12 parts by weight ofcyclopentane (Erdölchemie). The mixture (component A+cyclopentane)immediately becomes turbid and separates.

EXAMPLE 6

(not according to the invention)

Formulation for rigid polyurethane foam

Component A

55 parts by weight of polyol C

20 parts by weight of polyol D

25 parts by weight of polyesterpolyol Stepanpol® 2352 (Stepan)

2.3 parts by weight of water

2.0 parts by weight of silicone stabiliser

1.5 parts by weight of activator mixture consisting of activatorDesmorapid PV (Bayer AG) and activator Desmorapid 726b (Bayer AG)

100 parts by weight of component A are mixed with 11 parts by weight ofi,n-pentane (3:8). The mixture (component A+i,n-pentane) immediatelybecomes turbid and separates.

EXAMPLE 7

(according to the invention)

Formulation for rigid polyurethane foam

Component A

40 parts by weight of polyol C

20 parts by weight of polyol I

15 parts by weight of polyol K

25 parts by weight of polyesterpolyol Stepanpol® 2352 (Stepan)

2.4 parts by weight of water

2.0 parts by weight of silicone stabiliser

1.4 parts by weight of activator Desmorapid PV (Bayer AG)

0.4 parts by weight of activatorN,N′,N″-tris-(dimethylaminopropyl)hexahydrotriazine

100 parts by weight of component A are mixed at 20° C. with 15 parts byweight of cyclopentane (Erdölchemie) and 161 parts by weight of crudeMDI (Desmodur 44V20, Bayer AG) and compacted to 34 kg/m³ in a closedmould.

EXAMPLE 8

(according to the invention)

Formulation for rigid polyurethane foam

Component A

20 parts by weight of polyol C

40 parts by weight of polyol I

15 parts by weight of polyol K

25 parts by weight of polyesterpolyol Stepanpol® 2352 (Stepan)

2.4 parts by weight of water

2.0 parts by weight of silicone stabiliser

1.4 parts by weight of activator Desmorapid PV (Bayer AG)

0.4 parts by weight of activatorN,N′,N″-tris-(dimethylaminopropyl)hexahydrotriazine

100 parts by weight of component A are mixed at 20° C. with 15 parts byweight of cyclopentane (Erdölchemie) and 157 parts by weight of crudeMDI (Desmodur 44V20, Bayer AG) and compacted to 34 kg/m³ in a closedmould.

EXAMPLE 9

(according to the invention)

Formulation for rigid polyurethane foam

Component A

10 parts by weight of polyol C

50 parts by weight of polyol I

15 parts by weight of polyol K

25 parts by weight of polyesterpolyol Stepanpol® 2352 (Stepan)

2.4 parts by weight of water

2.0 parts by weight of silicone stabiliser

0.5 parts by weight of activator Desmorapid PV (Bayer AG)

0.5 parts by weight of activator dimethylaminopropylformamide

0.4 parts by weight of activatorN,N′,N″-tris-(dimethylaminopropyl)hexahydrotriazine

100 parts by weight of component A are mixed at 20° C. with 17 parts byweight of cyclopentane (Erdölchemie) and 170 parts by weight of MDIprepolymer (E577, Bayer AG) and compacted to 36 kg/m³ in a closed mould.

EXAMPLE 10

(according to the invention)

Formulation for rigid polyurethane foam

Component A

40 parts by weight of polyol C

10 parts by weight of polyol G

50 parts by weight of polyol I

2.5 parts by weight of water

2.0 parts by weight of silicone stabiliser

0.5 parts by weight of activator Desmorapid PV (Bayer AG)

1.6 parts by weight of activator Desmorapid 726b (Bayer AG)

100 parts by weight of component A are mixed at 20° C. with 13 parts byweight of cyclopentane (Erdölchemie) and 135 parts by weight of crudeMDI (Desmodur 44V20, Bayer AG) and compacted to 35 kg/m³ in a closedmould.

EXAMPLE 11

(according to the invention)

Formulation for rigid polyurethane foam

Component A

20 parts by weight of polyol C

45 parts by weight of polyol I

15 parts by weight of polyol K

20 parts by weight of polyesterpolyol Stepanpol® 2352 (Stepan)

2.4 parts by weight of water

2.0 parts by weight of silicone stabiliser

1.2 parts by weight of activator Desmorapid PV (Bayer AG)

0.4 parts by weight of activatorN,N′,N″-tris-(dimethylaminopropyl)hexahydrotriazine

100 parts by weight of component A are mixed at 20° C. with 13 parts byweight of i,n-pentane (3:8) and 151 parts by weight of MDI prepolymer(Desmodur 44V20, Bayer AG) and compacted to 35 kg/m³ in a closed mould.

The test values shown in the Table were obtained from the foam slabsproduced in Examples 1 to 11.

Phase stability of com- Thermal conduc- ponent A containing Fibre timeof tivity (mW/mK) to Example blowing agent foam (s) DIN 52616, 24° C. 1clear, stable mixture 50 19.6 2 clear, stable mixture 50 21.5 3 clear,stable mixture 29 21.6 4 clear, stable mixture 50 23.7 5 turbid,separated mixture — — 6 turbid, separated mixture — — 7 clear, stablemixture 25 19.9 8 clear, stable mixture 25 19.7 9 clear, stable mixture31 19.9 10 clear, stable mixture 27 19.9 11 clear, stable mixture 2822.0

Example 1 shows a typical result for an R11-reduced system.

Examples 2 and 3 are prior art cyclopentane-blown systems havingstandard thermal conductivities.

Although Example 3 contains a polyesterpolyether and an activatormixture according to the invention, which results in a fibre time of 29s, a standard thermal conductivity is found.

Example 4 is a prior art i,n-pentane-blown system.

Examples 5 and 6 contains no amine-started polyols; the polyolformulation is thus not phase-stable with regard to cyclopentane andcannot be foamed using conventional techniques.

Examples 7 to 10 show that, using the process according to the inventionwith cyclopentane as the blowing agent, foams are obtained having thesame low thermal conductivity as foams blown with reduced quantities ofR11.

Example 1 1 shows that foams having low thermal conductivities are alsoobtained using the process according to the invention with i,n-pentaneas the blowing agent.

What is claimed is:
 1. A process for the production of rigidpolyurethane foams having low thermal conductivity comprising reactingA) a polyol component comprising: (1) at least one polyester polyolhaving a molecular weight of from 100 to 30,000 g/mol and containing atleast two isocyanate-reactive hydrogen atoms; (2) at least one polyetherpolyol having a molecular weight of from 150 to 12,500 g/mol andcontaining at least two isocyanate-reactive hydrogen atoms and at leastone tertiary nitrogen atom, and being prepared by the polyaddition ofone or more alkylene oxides onto at least one starter compound, whereinthe starter compound comprises ammonia, or a compound containing atleast one primary, secondary or tertiary amino group; (3) at least onepolyether polyol having a molecular weight of from 150 to 12,500 g/moland containing at least two isocyanate-reactive hydrogen atoms, andbeing prepared by the polyaddition of one or more alkylene oxides ontoat least one starter compound, wherein the starter compound compriseswater or a polyhydric alcohol; (4) at least one catalyst; (5) water (6)at least one blowing agent selected from the group consisting ofn-butane, isobutane, isopentane, cyclopentane, 2,2-dimethylbutane,cyclohexane, and mixtures thereof; and, optionally (7) auxiliarysubstances and/or additives; with B) an organic polyisocyanate having anNCO group content of from 20 to 48% by weight, wherein saidpolyisocyanate is optionally modified.
 2. The process of claim 1,wherein A)(1) said polyester polyol having a molecular weight of from100 to 30,000 is prepared by reacting (i) one or more aromatic and/oraliphatic mono-, di- and tricarboxylic acids with (ii) one or morepolyols containing at least two hydroxyl groups.
 3. The process of claim1, wherein A)(2) comprises an o-tolylene-diamine initiated polyetherpolyol which contains from 70 to 100% by weight of 1,2-propylene oxideand from 0 to 30% by weight of ethylene oxide, with the percents byweight of 1,2-propylene oxide and ethylene oxide totaling 100%.
 4. Theprocess of claim 1, wherein A)(2) comprises an ethylenediamine initiatedpolyether polyol which contains from 50 to 100% by weight of1,2-propylene oxide and from 0 to 50% by weight of ethylene oxide, withthe percents by weight of 1,2-propylene oxide and ethylene oxidetotaling 100%.
 5. The process of claim 1, wherein A)(2) comprises atriethanolamine-initiated polyether polyol which contains from 50 to100% by weight of 1,2-propylene oxide and from 0 to 50% by weight ofethylene oxide, with the percents by weight of 1,2-propylene oxide andethylene oxide totaling 100%.
 6. The process of claim 1, wherein A)(3)comprises a sucrose-initiated polyether polyol which contains from 70 to100% by weight of 1,2-propylene oxide and from 0 to 30% by weight ofethylene oxide, with the percents by weight of 1,2-propylene oxide andethylene oxide totaling 100%.
 7. The process of claim 1, wherein A)(3)comprises a sorbitol-initiated polyether polyol which contains from 70to 100% by weight of 1,2-propylene oxide and from 0 to 30% by weight ofethylene oxide, with the percents by weight of 1,2-propylene oxide andethylene oxide totaling 100%.
 8. The process of claim 1, wherein A)(3)comprises a trimethylol propane-initiated polyether polyol whichcontains from 70 to 10% by weight of 1,2-propylene oxide and from 0 to30% by weight of ethylene oxide, with the percents by weight of1,2-propylene oxide and ethylene oxide totaling 100%.
 9. The process ofclaim 1, wherein A)(3) comprises a glycerol-initiated polyether polyolwhich contains from 70 to 100% by weight of 1,2-propylene oxide and from0 to 30% by weight of ethylene oxide, with the percents by weight of1,2-propylene oxide and ethylene oxide totaling 100%.
 10. The process ofclaim 1, wherein A)(5) water is present in an amount of from 0.5 to 7.0parts by weight, based on 100 parts by weight of component A).
 11. Theprocess of claim 1 herein A)(6) said blowing agent consists essentiallyof cyclopentane.
 12. The process of claim 1, wherein A)(6) said blowingagent is selected from the group consisting of cyclopentane, n-butane,isobutane, 2,2-dimethylbutane and mixtures thereof.
 13. The process ofclaim 1, wherein A)(6) said blowing agent is selected from the groupconsisting of isopentane, cyclopentane, cyclohexane and mixturesthereof.
 14. In a process for the production of a composite componentcomprising a rigid foam interlayer, the improvement wherein the rigidfoam interlayer comprises the rigid polyurethane foam produced by theprocess of claim 1.